The field of the invention pertains to passive solar heating and cooling devices. In particular, the invention pertains to thermal storage devices that form the wall, roof or window of a structure for the absorbtion and radiation of heat to or from the structure.
Masses of stone, water and other materials have been used for many years as solar thermal storage mediums. In the northern hemisphere the materials are incorporated in a generally south facting wall or roof of a home or other structure. To increase the effectiveness of such mediums, glazing may be positioned outside of the thermal storage medium with an air gap of several inches therebetween. During the day the thermal medium warms and during the night the medium radiates the stored heat into the structure.
SUch a simple system unfortunately radiates heat back through the glass to the night sky. The heat radiated to the structure interior is also not controllable. To overcome these problems, movable insulated blankets have been employed to cover the thermal medium and prevent radiation to the night sky.
Vents below and above a thermal storage wall have been employed to provide natural air circulation from the structure interior, through the air gap and back into the structure. The latter has become commonly known as a Trombe wall after the originator of the technique.
More recently a research project has tested rotatable thermal storage panels containing a phase changeable medium with insulation directly fastened on one side and a reflective surface on the opposite side. The panels are located behind double glazing. Such movable panels permit the amount of heat stored and the amount of heat radiated to the structure to be controlled by the positioning of the panel both during the daytime and the nighttime. The tests were published in the Proceedings of the 2nd National Passive Solar Conference Vol. II (Mar. 16-18, 1978) Illinois Institute of Technology.
A form of window shutters that are rotatable with light and heat reflecting surfaces on one side and light and heat absorbing surfaces on the other side are disclosed in U.S. Pat. No. 3,012,294. The shutters are inside transparent tubes to permit the passage of light to the interior in an intermediate position of the shutters.
The challenge is to develop more effective means to both maximize the insolation of passive thermal storage walls and effectively control the heat radiated and convected to the structure interior in winter. More effective means are also needed to passively cool the structure interior by natural convection and radiation in the summer.